The present invention relates generally to flexible abrasive products which include a backing which bears shaped abrasive structures, a method of making and using the same, and an apparatus for making the same.
1. Background Art
Abrasive products are available in any of a variety of types, each generally being designed for specific applications and no particular type providing a universal abrading tool for all applications. The various types of abrasive products include, for example, coated abrasives, bonded abrasives, and low density or nonwoven abrasive products (sometimes called surface conditioning products). Coated abrasives typically comprise abrasive granules generally uniformly distributed over and adhered to the surface of a flexible backing. Bonded abrasives, a typical example of which is a grinding wheel, generally comprises abrasive material rigidly consolidated together in a mass in the form of a rotatable annulus or other shapes such as a block-shaped honing stone. Low density or nonwoven abrasive products typically include an open, lofty, three-dimensional fiber web impregnated with adhesive which does not alter the open character of the web and also adheres abrasive granules to the fiber surfaces of the web.
Bonded abrasive products such as grinding wheels are very rigid and, thus, not conformable to workpieces which have a complex surface. Coated abrasives are often used as abrasive belts or abrasive discs. Coated abrasive belts and discs have a high initial cut rate and produce a high surface roughness when new, but each of these properties drops off very rapidly in use. Coated abrasive products also have a somewhat limited degree of conformability when they are supported in an abrading machine. While use of abrasive belts on soft back-up wheels provides some degree of conformability, the lack of stretchability of the coated abrasive backing limits somewhat its conformability.
Abrasive products are used industrially, commercially, and by individual consumers to prepare any of a variety of materials for use or for further processing. Exemplary uses of abrasive products include preliminary preparation of a surface before priming or painting, cleaning the surface of an object to remove oxidation or debris and grinding or abrading an object to obtain a specific shape. In these applications, abrasive products may be used to grind a surface or workpiece to a certain shape or form, to abrade a surface to clean or to facilitate bonding of a coating such as paint, or to provide a desired surface finish, especially a smooth or otherwise decorative finish.
The grinding or finishing properties of the abrasive product may be tailored to some degree to provide a desired aggressive level of removal of material from a surface being abraded (xe2x80x9ccutxe2x80x9d), balanced with the need for a particular surface finish (xe2x80x9cfinish)xe2x80x9d. These needs may also be balanced with the need for a relatively long, useful life for the abrasive product. Typically, however, the cut and finish performance during the useful life of an abrasive product is not as consistent as desired. That is, during the useful life of typical abrasive products, the cut and finish of the product may vary with cumulative use. A need, therefore, exists for abrasive products with increased consistency of cut and finish. Such new products that also bridge the cut and finish performance between coated abrasive products and surface conditioning products would be especially useful.
Many methods of making abrasive products employ liquid or solvent-borne volatile organic binder materials which result in the unwanted creation of volatile organic compound (VOC) emissions. Some binder materials are water-borne and, thus, require an unwanted expense because of the additional energy cost in removing the water. Moreover, some methods of making abrasive products are complex, requiring multiple steps and complex equipment. A simplified process to produce such new abrasive products providing economical short product cycles and low or minimal volatile organic waste products would be particularly useful.
Thus, need exists for a flexible abrasive product which has a tailored cutting ability and a long, useful life which can be made in a simple method without producing undesirable amounts of volatile organic compound waste products.
2. Other Related Art
U.S. Pat. No. 2,115,897 (Wooddell et al.) teaches an abrasive article having a backing having attached thereto by an adhesive a plurality of bonded abrasive segments. These bonded abrasive segments can be adhesively secured to the backing in a specified pattern.
U.S. Pat. No. 3,048,482 (Hurst) discloses an abrasive article comprising a backing, a bond system and abrasive granules that are secured to the backing by the bond system. The abrasive granules are a composite of abrasive grains and a binder which is separate from the bond system. The abrasive granules are three dimensional and are preferably pyramidal in shape. To make this abrasive article, the abrasive granules are first made via a molding process. Next, a backing is placed in a mold, followed by the bond system and the abrasive granules. The mold has patterned cavities therein which result in the abrasive granules having a specified pattern on the backing.
U.S. Pat. No. 3,605,349 (Anthon) pertains to a lapping type abrasive article. Binder and abrasive grain are mixed together and then sprayed onto the backing through a grid. The presence of the grid results in a patterned abrasive coating.
Great Britain Patent Application No. 2,094,824 (Moore) pertains to a patterned lapping film. The abrasive/binder resin slurry is prepared and the slurry is applied through a mask to form discrete islands. Next, the binder resin is cured. The mask may be a silk screen, stencil, wire or a mesh.
U.S. Pat. Nos. 4,644,703 (Kaczmarek et al.) and 4,773,920 (Chasman et al.) concern a lapping abrasive article comprising a backing and an abrasive coating adhered to the backing. The abrasive coating comprises a suspension of lapping size abrasive grains and a binder cured by free radical polymerization. The abrasive coating can be shaped into a pattern by a rotogravure roll.
Japanese Patent Application No. JP 62-238724A (Shigeharu, published Oct. 19, 1987) describes a method of forming a large number of intermittent protrusions on a substrate. Beads of pre-cured resin are extrusion molded simultaneously on both sides of the plate and subsequently cured.
U.S. Pat. No. 4,930,266 (Calhoun et al.) teaches a patterned abrasive sheeting in which the abrasive granules are strongly bonded and lie substantially in a plane at a predetermined lateral spacing. In this invention the abrasive granules are applied via an impingement technique so that each granule is essentially individually applied to the abrasive backing. This results in an abrasive sheeting having a precisely controlled spacing of the abrasive granules.
U.S. Pat. No. 5,014,468 (Ravipati et al.) pertains to a lapping film intended for ophthalmic applications. The lapping film comprises a patterned surface coating of abrasive grains dispersed in a radiation cured adhesive binder. To make the patterned surface an abrasive/curable binder slurry is shaped on the surface of a rotogravure roll, the shaped slurry removed from the roll surface and then subjected to radiation energy for curing.
U.S. Pat. No. 5,107,626 (Mucci) teaches a method of providing a patterned surface on a substrate by abrading with a coated abrasive containing a plurality of precisely shaped abrasive composites. The abrasive composites are in a non-random array and each composite comprises a plurality of abrasive grains dispersed in a binder.
Japanese Patent Application No. 02-083172 (Tsukada et al., published Mar. 23, 1990) teaches a method of a making a lapping film having a specified pattern. An abrasive/binder slurry is coated into indentations in a tool. A backing is then applied over the tool and the binder in the abrasive slurry is cured. Next, the resulting coated abrasive is removed from the tool. The binder can be cured by radiation energy or thermal energy.
Japanese Patent Application No. JP 4-159084 (Nishio et al., published Jun. 2, 1992) teaches a method of making a lapping tape. An abrasive slurry comprising abrasive grains and an electron beam curable resin is applied to the surface of an intaglio roll or indentation plate. Then, the abrasive slurry is exposed to an electron beam which cures the binder and the resulting lapping tape is removed from the roll.
U.S. Pat. No. 5,190,568 (Tselesin) describes a coated abrasive having a plurality of peaks and valleys. Abrasive particles are embedded in and on the surface of the composite structure.
U.S. Pat. No. 5,199,227 (Ohishi) describes a surface treating tape comprising a plurality of particulate filled resin protuberances on a substrate. The protuberances are closely spaced Bernard cells coated with a layer of premium abrasive particles.
U.S. Pat. No. 5,435,816 (Spurgeon et al.), assigned to the same assignee as the present application, teaches a method of making an abrasive article. In one aspect of this patent application, an abrasive/binder slurry is coated into recesses of an embossed substrate. Radiation energy is transmitted through the embossed substrate and into the abrasive slurry to cure the binder.
U.S. Pat. No. 5,437,754 (Calhoun), assigned to the same assignee as the present application, teaches a method of making an abrasive article. An abrasive slurry is coated into recesses of an embossed substrate. The resulting construction is laminated to a backing and the binder in the abrasive slurry is cured. The embossed substrate is removed and the abrasive slurry adheres to the backing.
U.S. Pat. No. 5,672,097 (Hoopman), assigned to the same assignee as the present application, teaches an abrasive article where the features are precisely shaped but vary among themselves.
European Patent No. 702,615 (Romero, published Oct. 22, 1997) describes an abrasive article having a patterned abrasive surface. The abrasive article has a plurality of raised and recessed portions comprising a thermoplastic material, the raised portions further comprising a layer of adhesive and abrasive material while the recessed portions are devoid of abrasive material.
U.S. Pat. No. 5,785,784 (Chesley et al.) pertains to an abrasive article having a first and a second, opposite, major surface. A mechanical fastener is formed on one surface and precisely shaped abrasive composites are applied via a production tool on the opposite major surface.
U.S. Pat. No. 6,299,508 (Gagliardi et al.) describes an abrasive article having a plurality of grinding-aid containing protrusions integrally molded to the surface of a backing. The protrusions are contoured so as to define a plurality of peaks and valleys, wherein abrasive particles cover at least a portion of the peaks and valleys.
U.S. Pat. No. 5,976,204 (Hammarstrom, et al.) describes a method of making abrasive articles of a consolidated matrix of abrasive grain granules, wherein the abrasive grain granules have a continuous uniform surface coating of an organic bond.
U.S. Pat. No. 5,611,827 (Hammarstrom, et al.) describes a method of preparing mixtures for abrasive articles by blending an abrasive material with a liquid binder material to produce a flowable granular material coated with a phenol-novolac resin bond which can be molded to make abrasive grinding wheels.
U.S. Pat. No. 5,681,361 (Sanders) describes a method of making an abrasive article, where abrasive particles are adhesively attached in a uniform manner to an organic substrate that avoids the use of organic solvent compounds. In one aspect, the invention describes contacting an organic substrate with a dry particulate material comprising a plurality of fusible organic binder particles and a plurality of abrasive particles, liquefying said organic binder particles to provide a flowable liquid binder, and solidifying said flowable liquid binder to bond the dispersed abrasive particles with the substrate.
U.S. Pat. No. 6,228,133 (Thurber et al.) teaches the use of powder coating methods to form coated abrasives. The powder exists as a solid under desired dry coating conditions, but is easily melted at relatively low temperatures and then solidified also at reasonably low processing temperatures to form abrasive make coats, size coats and/or supersize coats, as desired.
U.S. Pat. No. 5,578,098 (Gagliardi et al.) describes a coated abrasive article comprising a backing with bearing on at least one major surface erodible agglomerates and abrasive grains, wherein the erodible agglomerates consist essentially of a grinding aid and the erodible agglomerates are in the form of rods. The erodible agglomerates can be between or above or between and above the abrasive grains.
U.S. Pat. No. 5,039,311 (Bloecher) pertains to an erodible granule comprising: (a) an erodible base agglomerate comprising first abrasive grains in a binder (preferably resinous adhesives, inorganic adhesives or metal adhesives); and (b) over at least a portion of said base agglomerate, a coating (preferably at least 2 coatings) comprising a plurality of second abrasive grains bonded to said base agglomerate, said abrasive granule and said base agglomerate having sufficient strength to withstand abrading forces. A coated abrasive article comprises the above abrasive granules (preferably secured to a backing by a make coat and size coat), as do a bonded abrasive article and a non-woven abrasive article.
U.S. Pat. No. 4,486,200 (Heyer et al.) teaches a method of making an abrasive article comprising a plurality of separated abrasive agglomerates distributed within a matrix of undulated filaments. The preferred method of forming said abrasive agglomerates within a lofty open web involves depositing a pattern of spaced agglomerates formed of a mixture of liquid bonding agent and abrasive granules with an appropriate printing or extruding device and curing the agglomerates.
The invention provides an abrasive product, a method of making the same without creating substantial quantities of unwanted volatile organic compound emissions or water evaporation expense and a method of using the same. The invention also provides an apparatus for making the abrasive product.
The novel abrasive product includes a flexible backing onto which is bonded a plurality of shaped structures comprised of abrasive particles adhered together with a cured binder material.
In one aspect, the invention provides a method of making an abrasive product comprising:
a. providing a substantially horizontally deployed flexible backing having a first surface bearing an at least partially cured primer coating and an opposite second surface;
b. providing a dry flowable particle mixture comprising abrasive particles and particulate curable binder material;
c. depositing a plurality of temporary shaped structures comprised of said particle mixture on the at least partially cured primer coating of the first surface of the backing;
d. softening said particulate curable binder material to provide adhesion between adjacent abrasive particles; and
e. curing the softened particulate curable binder material to convert said temporary shaped structures into permanent shaped structures and cure the at least partially cured primer coating on the first surface of the backing.
The invention further provides a flexible abrasive product which comprises:
a. a flexible backing having a first surface bearing a primer coating, an opposite second surface and opposite ends; and
b. a plurality of shaped structures each structure having a distal end spaced from said backing and an attachment end attached to the primer coating on the backing, said shaped structures being comprised of abrasive particles and cured particulate binder.
The invention also provides an apparatus for making a flexible abrasive product comprising:
a. a frame for supporting and dispensing a flexible backing having a first surface and an opposite second surface with the first surface deployed in a substantially horizontal deployment;
b. a primer dispensing system for depositing curable primer material over the first surface of the backing;
c. a primer curing system for at least partially curing the curable primer material to provide a primer coating on the first surface of the backing;
d. a dispensing apparatus for receiving a mixture of particulate curable binder material and abrasive particles and depositing a plurality of temporary shaped structures comprised of the mixture of particulate curable binder material and abrasive particles on the at least partially cured primer coating of the first surface of the backing;
e. a particulate binder softening system for softening the particulate curable binder so that it will adhere adjacent abrasive particles; and
f. a particulate binder curing system for curing the particulate curable binder material and for curing the at least partially cured primer coating to convert said temporary shaped structures into permanent shaped structures adhered to the cured primer coating on the first surface of the backing.
The invention also provides a method of abrading a surface of a workpiece. The method comprises:
a. providing an abrasive product comprising:
i. a flexible backing having a first surface bearing a cured primer coating, an opposite second surface and opposite ends; and
ii. a plurality of shaped structures each structure having a distal end spaced from said backing and an attachment end attached to the primer coating on the backing, said shaped structures being comprised of abrasive particles and cured particulate binder;
b. contacting the surface of the workpiece with the distal ends of the shaped structures; and
c. relatively moving at least one of said workpiece or said abrasive product while providing sufficient force between the workpiece surface and the distal ends of the shaped structures of the abrasive product to abrade and/or otherwise modify the surface.
The invention further provides:
A flexible abrasive product comprising:
a. a flexible backing having a first surface bearing a primer coating, an opposite second surface and opposite ends; and
b. a plurality of shaped structures each structure having a distal end spaced from said backing and an attachment end attached to the primer coating on the backing, said shaped structures being comprised of abrasive particles and organic binder, said abrasive product having on average substantially consistent, high cut levels, after an initial cut cycle, compared to conventional coated abrasive products.
The term xe2x80x9cbackingxe2x80x9d shall mean a flexible sheet material which will withstand use conditions of an abrasive product of the type herein described.
The term xe2x80x9cshaped structuresxe2x80x9d shall mean a structure having three dimensions including height, width and depth such as a cube, rectangular block, right cylinder, rib, truncated cone or truncated pyramid.
The term xe2x80x9ctemporary shaped structurexe2x80x9d shall mean a shaped structure comprised of components in a transitory state which may be easily deformed by slight contact until it is converted to a permanent shaped structure.
The term xe2x80x9cparticulate curable binder materialxe2x80x9d shall mean binder materials which are solid at room temperature, have been processed to provide particles, and which may be softened and cured either upon heating and subsequent cooling, if thermoplastic, or upon sufficient exposure to heat or other suitable energy source, if thermosetting or cross-linkable.
The term xe2x80x9ccured particulate binderxe2x80x9d shall mean a binder that was formerly particulate which has been softened and cured to form a cured mass of binder which no longer has particulate characteristics.
The term xe2x80x9cat least partially cured primerxe2x80x9d with reference to the primer coating shall mean the material forming the primer coating is sufficiently cohesive to be handleable but not fully cross-linked, if thermosetting, or not fully fused, if thermoplastic.
The term xe2x80x9cpermanent shaped structurexe2x80x9d shall mean a shaped structure which will not be altered by slight contact except when it is employed to abrade or otherwise modify the surface of a workpiece.
The term xe2x80x9csofteningxe2x80x9d with reference to the particulate binder material shall mean converting the particulate binder material from a solid having a defined particle shape to a physical form which no longer has the defined shape but instead is flowable as a liquid, viscous liquid, or semi-liquid mass.
The term xe2x80x9ccuredxe2x80x9d with reference to the curable binder or primer material means that the material has been hardened to such a degree that the resulting product will function as an abrasive product.
The term xe2x80x9csubstantially horizontally deployedxe2x80x9d with reference to the deployment of the backing shall mean deployed in a manner so that a temporary shaped structure comprised of a dry particulate mixture deposited on a surface of the backing will not be altered in shape because of particle movement caused by any incline from actual horizontal of the backing deployment. That is, the backing may be deployed moderately from an actual horizontal deployment.
The term xe2x80x9cdry,xe2x80x9d when used to describe the particulate curable binder material, means essentially free of liquid phase substances to the extent that the particulate curable binder material remains particulate, although a minor amount of a liquid may be added as a modifier which typically will not alter the particulate character of the particulate curable binder material.